1. Field of the Invention
The present invention relates to a trajectory displaying device having a function for displaying trajectories of a motor end and a machine end.
2. Description of the Related Art
In the prior art, as a method for monitoring an error in a shape of a machined object, a tool trajectory displaying method has been used, wherein a commanded trajectory of a representative point (such as a tool center point) of a machine tool and a feedback trajectory obtained when the representative point is actually moved according to the command are overlapped and displayed so that an error of the feedback trajectory relative to the commanded trajectory is visually monitored.
For example, JP H06-059717 A discloses an NC device having a function for overlapping a movement trajectory of a tool generated by analyzing an NC program with positional data obtained when the tool is moved according to the movement trajectory.
In the prior art, when an actual trajectory of a machine end measured by a measuring instrument configured to measure a trajectory of the machine end is compared to an actual trajectory of a motor end calculated from positional data of the motor end, the respective actual trajectories are displayed on separate indicators, etc. In this regard, when the actual trajectory of the machine end is fluctuated (or deviated from a command trajectory), such fluctuation may be due to either of two factors, i.e., a fluctuation of the position (trajectory) of the motor end, or, a fluctuation (or a mechanical error) of a mechanism for transmitting the motion of the motor end to the machine end. Therefore, it is difficult to discriminate one factor from another, merely by monitoring trajectory data of the machine end. Further, when the actual trajectories of the machine end and the motor end are separately displayed, it is difficult to compare and analyze the trajectories.
In the technique disclosed in JP H06-059717 A, a movement trajectory of a tool generated by an NC program and an actual trajectory of the tool obtained when the tool is moved based on the movement trajectory are displayed while being overlapped with each other. In other words, the NC device in JP H06-059717 A has a function for overlapping the feedback trajectory with the command trajectory, but is not configured to overlap two different types of actual trajectories with each other.